Trackline Report (Encrypted)

Introduction/Additional information:

Introduction

The Trackline Report (SPR) communicates a search pattern from the mission controller to a SRU (either to transmit a pattern for action or to cancel a pattern) or from a SRU to the MC (reporting acceptance or completion).

Summary of changes:

Version 0:

This is an RTCM compliant update of the FID 3 message listed in the Oct 2014 EAIS IDD. The FID was changed to avoid confusion with previously published message definitions.

There are AIS Message 25 and 8 variants of this message, but the encrypted message 8 is not implemented.

Permitted as from:

12/05/2016

Registrant:

USCG

Physical link:

AIS

Message number (0=VDES-VDE):

DAC or VPFI:

366

FI / Message ID:

Version:

State:

in force

State link:

Track Line Search Pattern, Route or Polygon, Overlay Option 2 [1]

Number of slots (max):

Last modified:

29/01/2021 - 23:19

Used by:

USCG

Details:

Encrypted Trackline Report Segment 1 (Message 26, Broadcast)

	Parameter		# of Bits	Description

Standard Message Header	Message ID		6	Identifier for Message 26; always 26.
	Repeat Indicator		2	Indicates how many times a message has been repeated. 0 – 3; 0 = default; 3 = do not repeat any more. Set to zero (default).
	Source MMSI		30	MMSI number of source station. Varies according to the transmitter ID.
	Destination Indicator		1	0 = Broadcast (no Destination ID field used) 1 = Addressed (Destination ID uses 30 data bits for MMSI) Set to 0, broadcast.
	Binary Data Flag		1	0 = unstructured binary data (no Application Identifier bits used); 1 = binary data coded as defined by using the16-bit Application identifier. Set to 1, structured.
Binary Data	Designated Area Code		10	Designated area code (DAC). This code is based on the maritime identification digits (MID). Set to 366.
	Function Identifier		6	Function identifier. Set to 15.
	Encrypted Payload	Version	3	Sequential number used to indicate the message version in steps of 1. 0 = test message = default; 1 – 7 = message version. Set to zero.
		Message Linkage ID	10	Identifier for the SAR Pattern Report. This number uniquely identifies a search pattern sent from a given SMC (MMSI) and is used to connect additional information with the search. Source MMSI and this ID uniquely identify the event. Set to 1 - 1023 by message originator; 0 = not available.
		Message Segment	5	Number of this message segment; sequential number. Recipient will need to receive all segments and put in order sequentially. 0 – 31. Set to 0.
		Number of Segments	5	Total number of segments comprising the complete Trackline Report (Total = N+1). N = 0- 31.
		Pattern Type	2	Type of search pattern: 0 = Trackline Search Pattern or route = default; 1 = Polygon; 2-3 = reserved.

Code	From MC	From Action SRU
0	Search plan to be executed	Search plan to be executed (concur w/ mission plan, and will take FORAC)
1	Reserved	Search plan started (time and search position updated to actual CST and CSP)
2	Reserved	Search plan completed. (time and point updated to reflect completion time and last position)
3	Search plan cancelled by SMC	Search plan aborted (time and point updated to reflect aborted time and position)
4	Directions to divert from search plan at this position, execute new search plan.	Indicates unit has diverted from search plan at this position
5	Direction to resume search plan at this position	Indicates the unit has resumed search plan at this position
6	Reserved	Reserved for future use
7	Reserved	Unable to execute search plan

Encrypted Payload

Search Pattern Status

Reference Time

UTC Day

1 – 31; 0 = UTC day not available = default.

UTC Hour

UTC Hour.

0 – 23; 24 = UTC hour not available = default; 25 - 31 = reserved.

UTC Min

UTC Minute.

0 – 59; 60 = UTC minute not available = default; 61 - 63 (reserved for future use).

Action SRU MMSI

MMSI of the Action SRU. This varies according to the MMSI of the desired unit. 0

= unknown = default;

Case ID Number

Case ID. Maximum 5 characters 6-bit ASCII as defined in ITU 1371-5, Table 47. “@@@@@” = not available = default.

If less than 5 characters, the remainder of the parameter should be filled with “@” characters (set bits to 0); but, not shown on the presentation.

Search Point

Longitude

Longitude in 1/10,000 minute. (±180°)

East = positive (as per 2’s complement); West = negative (as per 2’s complement); 181° = not available = default.

Latitude

Latitude in 1/10,000 minute (±90°)

North = positive (as per 2’s complement); South = negative (as per 2’s complement); 91° = not available = default.

Search Altitude

Altitude for search pattern in 50 ft increments.

0 = sea level; 50 – 6000 ft; 121 = not specified = default; 122 – 127 = reserved.

Search Speed

Speed to execute the search pattern in 1kt increments. 0 = not specified = default; 1 – 500 kts;

501 – 510 = reserved; 511 – not to be used.

Encryption Bit Padding

Sufficient spare bits to ensure that the binary data is a multiple of 128 bits for block encryption (256). Set to 0.

Checksum

16-bit CRC calculated as per EAIS Specification

Footer	Spare	4	Four extra bits added to ensure the message ends on a byte boundary. Set to zero.
	Communications State Selector	1	0 = SOTDMA communication state follows, 1 = ITDMA communication state follows
	Communications State	19	SOTDMA communication state (see ITU 1371-5 § 3.3.7.2.1, Annex 2), if communication state selector flag is set to 0, or ITDMA communication state (§ 3.3.7.3.2, Annex 2), if communication state selector flag is set to 1.
Total bits		352	2 Slot Binary Message

Encrypted Trackline Report Segment 2-32 (Message 26, Broadcast)

Parameter				# of Bits	Description
Standard Message Header	Message ID			6	Identifier for Message 26; always 26.
	Repeat Indicator			2	Indicates how many times a message has been repeated. 0 – 3; 0 = default; 3 = do not repeat any more. Set to zero (default).
	Source MMSI			30	MMSI number of source station. Varies according to the transmitter ID.
	Destination Indicator			1	0 = Broadcast (no Destination ID field used), 1 = Addressed (Destination ID uses 30 data bits for MMSI) Set to 0, broadcast.
	Binary Data Flag			1	0 = unstructured binary data (no Application Identifier bits used); 1 = binary data coded as defined by using the16-bit Application identifier. Set to 1, structured.
Binary Data	Designated Area Code			10	Designated area code (DAC). This code is based on the maritime identification digits (MID). Set to 366.
	Function Identifier			6	Function identifier. Set to 15.
	Encrypted Payload	Version		3	Sequential number used to indicate the message version in steps of 1. 0 = test message = default; 1 – 7 = message version. Set to zero.
		Message Linkage ID		10	Identifier for the SAR Pattern Report. This number uniquely identifies a search pattern sent from a given SMC (MMSI) and is used to connect additional information with the search. Source MMSI and this ID uniquely identify the event. Set to 1 - 1023 by message originator; 0 = not available.
		Message Segment		5	Number of this message segment; sequential number. Recipient will need to receive all segments and put in order sequentially. 1 – 31.
		Number of Segments		5	Total number of segments comprising the complete Trackline Report (Total = N+1). N = 0- 31.
		Search Point	Longitude	28	Longitude in 1/10,000 minute. (±180°) East = positive (as per 2’s complement); West = negative (as per 2’s complement); 181° = not available = default.
			Latitude	27	Latitude in 1/10,000 minute (±90°) North = positive (as per 2’s complement); South = negative (as per 2’s complement); 91° = not available = default.
		Search Altitude		7	Altitude for search pattern in 50 ft increments. 0 = sea level; 50 – 6000 ft; 121 = not specified = default; 122 – 127 = reserved.
		Search Speed		9	Speed to execute the search pattern in 1kt increments. 0 = not specified = default; 1 – 500 kts; 501 – 510 = reserved; 511 – not to be used.
		Encryption Bit Padding		34	Sufficient spare bits to ensure that the binary data is a multiple of 128 bits for block encryption (128). Set to 0.
	Checksum			16	16-bit CRC calculated as per EAIS Specification

Footer	Spare	4	Four extra bits added to ensure the message ends on a byte boundary. Set to zero.
	Communications State Selector	1	0 = SOTDMA communication state follows 1 = ITDMA communication state follows
	Communications State	19	SOTDMA communication state (see ITU 1371-5 § 3.3.7.2.1, Annex 2), if communication state selector flag is set to 0, or ITDMA communication state (§ 3.3.7.3.2, Annex 2), if communication state selector flag is set to 1.
Total bits		224	2 Slot Binary Message

1. 1. Usage Notes
    - The SAR execution status is controlled by the SAR Pattern Status field. A State Diagram is shown in Figure 1 with the execution flow as follows:
      - The pattern is initially sent from the SMC to the action SRU with the Status set as 0 (direction to execute a plan).
      - The SRU should respond with either:
        
        Status set as 0 to indicate that the pattern was received and will be started (identical pattern parameters).
        
        Status set to 7 to say the pattern cannot be executed.
      - If the SRU sends a status of 7 the SMC needs to send a new pattern (followed up with communications between the MC and SRU to discuss WHY the pattern cannot be executed).
      - Once the search plan is started the SRU shall send a message with status 1 with the time and position fields updated to reflect the actual commence search time and position.
      - Once the pattern is complete the SRU should send the SAR pattern report with a status of 2 and with the time and position fields updated to reflect time and position of completion.
      - If the SRU needs to abort the plan prior to completion a message with status=3 should be sent with the time and position fields updated to reflect time and position when aborted plan.
      - If the SMC wants to cancel a SAR pattern prior to completion then the message is sent with status of 3.
    - The Message Linkage ID can be used to link additional text (e.g., a separate Linked Text message). However, the same source MMSI needs to be included in both the SPR and the Linked Text Message (LTM). This could be used to communicate a SAR pattern designation or additional notes about the pattern or search object.
    - A message version number is encoded as part of the message; if the received version number is different than what the display system has been programmed for, then the charting system should alert the user to the difference.
    - Positions are in WGS 84 Datum.

- - - If less than 10 characters, the remainder of the SRU designation parameter should be filled with “@” characters (set bits to 0); but, not shown on the presentation.
    - To allow the SRU to transmit the message it should be kept to a maximum of 3 slots, which equates to a maximum of 7 additional waypoints for unencrypted and 6 for the encrypted version.
    - A trackline search pattern is specified by the waypoints (Lat/Long).
    - If pattern type is polygon then the track connects back to the CSP.
    - The Trackline Report is sent as several short message segments that need to be assembled by the recipient. The segments are identified by segment number and list the total number of segments (1 of 3, 2 of 3 etc.).
    - The first Trackline Report segment contains the information about the type of pattern and search parameters. All succeeding segments just contain waypoint information.

Attachment:

eais_idd_v5_4_8may17.pdf [2]